Because of the increasing popularity of unrestrained access to broadband services by, for example, portable computing devices, there is an increasing need to extend the range of nodes such as access points associated with wireless networks, including but not limited to WLANs and wireless metropolitan area networks (WMANs) described and specified, for example, in the 802.11, 802.16 and 802.20 standards. The effective proliferation of wireless networks depends heavily on sustaining and increasing performance levels as user demands increase and supporting normal user activities such as movement or “roaming” within coverage areas while preserving connection integrity and quality of service (QoS) parameters.
One common practice in the mobile wireless industry to increase the range of wireless systems is through the use of repeaters. Various repeaters are known in the art operating at layer 1, commonly referred to as the physical layer (PHY), or above layer 1. Operation of a repeater at layers above layer 1, however, can cause significant performance issues when time sensitive data or data associated with high bandwidth applications is being transported by the network or can give rise to other modified in conventional layer 2 or higher operation, security features can be compromised along with a reduction in the overall ease of use.
In particular, an 802.11 repeater can extend the range of a given 802.11 Basic Service Set (BSS) by performing a cross-channel repeating function at the baseband level with little or no signal modulation/demodulation. The benefit of such a simplified approach is that repeating is performed in a very fast, low latency manner, while minimizing the overall silicon requirements for the underlying circuitry, thus providing a relatively inexpensive product solution. It will be appreciated that such repeater solutions works quite well for relatively fixed client stations with RF “visibility” to one of the Access Point (AP) or the repeater node, but not both.
Problems can arise however when the client has visibility to both the AP and the repeater node. In particular, a protocol-related problem arises when clients have clear visibility to both the AP and the repeater node during initialization or when roaming is imminent based on, for example, repeating a beacon frame having an identifier associated with the AP on a channel different from the designated channel. To better understand the problem, it should be noted that a typical repeater, as part of the repeating operation, will repeat an identifier associated with the AP, commonly referred to as the basic service set identifier (BSSID), on a channel other than the original transmit channel associated with the AP. By broadcasting the BSSID of the AP on a channel other than the original channel, one of the basic assumptions of the 802.11 protocol is violated. It should be noted that the basic rules of the protocol are encoded into virtually all 802.11-compliant stations implementations and rely on the uniqueness of the BSSID for identifying the BSS associated with a single channel. As will be appreciated, if only one of the AP or the repeater is visible to the client, the client can operate satisfactorily without knowledge of the protocol violation. If, on the other hand, the client can receive the beacon frame from both the AP and the repeater, problems can ensue as will be described herein below.
To understand the impact of violating the BSSID channel uniqueness assumption, it should be appreciated that in accordance with protocol operation, a table is generally kept of BSSID information including the channel information. Thus, during, for example, the building of a table of known BSSIDs, a table entry for a given BSSID will be created and associated with the first channel that the BSSID is received from. If the same BSSID is received on a different channel, the table entry will be subsequently updated or overwritten with the new channel information. The effect of overwriting the table entry will be to hide the original BSSID channel preventing the roaming client from scanning for optimal channel. The ultimate effect is that the roaming client will always join the BSSID/channel that was scanned most recently, never having the ability to compare additional BSSID/channels to determine which BSSID/channel is a better choice.
It would be desirable therefore for a physical layer repeater that can address and resolve the above identified problems and issues. Resolving these issues in such an exemplary repeater would preferably not result in substantial additional costs or complexity. Further the resolution of the above identified issues should be consistent with continued support of protocol operation, for example, in accordance with the 802.11 protocol or other protocols.